A compact eight-channel multiplexer with independently switchable passbands has been presented and investigated. The use of the dual-mode stub-loaded resonators can lead to significant size reduction for the multiplexer, this is because the required resonator number is reduced. In addition, the multiplexer is designed based on the distributed coupling technique, so that each passband can be designed individually due to the loading effect is small. Moreover, the complicated nine-port matching network at the input is not required. Besides, since the p-i-n diodes are connected to the output resonators for each channel, all passbands of the multiplexer can be independently switched on and off when the diode is in the reverse-biased and forward-biased states, respectively. Therefore, the proposed multiplexer can arbitrarily transfer to a single-band bandpass filter, a diplexer, a triplexer, a quadruplexer, a quinqueplexer, a sexaplexer, a septiplexer, and an octoplexer. For a demonstration, an eight-channel multiplexer with the second-order bandpass response have been designed and fabricated with microstrip in printed circuit board. The measured results are in good agreement with the full-wave simulation results.